Cardiovascular Physiology Part 3 Flashcards
What is the pacemaker potential?
An unstable resting potential in autorhythmic cells that gradually depolarizes towards threshold.
What ion permeability is high during the initial part of the pacemaker potential?
K⁺ permeability.
What happens to the permeability of a specific ion during the later part of the pacemaker potential, leading to depolarization?
Increased permeability to Ca²⁺ (T-type channels open).
What type of calcium channels are responsible for the rapid depolarization phase of the SA node action potential once threshold is reached?
Fast Ca²⁺ channels open.
How much does the AV node delay the impulse?
Approximately 0.1 seconds
Describe the path of the impulse from the atria to the ventricles.
Impulse passes from atria to ventricles via the AV bundle to Purkinje fibers and finally to the myocardial fibers.
What does ECG stand for and what does it record?
ECG records the electrical activity of the heart (electrical events in the myocardium) that can be correlated with mechanical events.
What does the P wave represent on an ECG?
trial depolarization (signals onset of atrial contraction).
What does the QRS complex represent on an ECG?
Ventricular depolarization (signals onset of ventricular contraction).
What does the T wave represent on an ECG?
Repolarization of ventricles.
What is the normal duration of the PR interval (or PQ interval)?
0.16 seconds.
What does the PR interval (or PQ interval) represent?
Extends from the start of atrial depolarization to the start of ventricular depolarization (QRS complex).
What mechanical events occur during the PR interval (or PQ interval)?
Atria contract and begin to relax.
What can an abnormal PR interval (greater than 0.20 seconds or 200 ms) indicate?
Can indicate damage to the conducting pathway or AV node.
What does the Q-T interval represent?
The time required for the ventricles to depolarize and repolarize.
